Implement for measuring or marking workpieces

ABSTRACT

This implement comprises an upright standard and a cross bar which extends at right angles to the standard and is adjustable to different heights along the standard and also in its axial direction so that its tool-carrying end may be extended to different distances from the standard. The invention provides that the cross bar is made of a tubular shape with closed ends which are connected to each other by bracing means, for example, tie rods, which extend longitudinally through the hollow inside of the cross bar and at least one of which is connected to at least one end of the cross bar at a point above the longitudinal axis of the cross bar so that, when this bracing means is tightened on the outside of one end of the cross bar, the toolcarrying part will be given a biasing tension which tends to curve this part upwardly and thereby counteracts the tendency of this part to bend downwardly under its own weight and the weight of the respective tool thereon. This biasing tension of the cross bar may be adjusted in accordance with the weight of the particular tool. By providing several tie rods or similar bracing means within the cross bar and connecting them at different points to the ends of the cross bar, and adjusting them axially to different tensions, the cross bar may also be bent in lateral directions.

iJnite States atent 1 111 3,722,42

Schweizer 1 Mar. 27, 1973 [54] IMPLEMENT FOR MEASURING OR 7 PrimaryExaminerMarion Parsons, Jr.

MARKING WORKPIECES AttorneyMichael s. Striker [75] Inventor: flirt-granSchweizer, Esslingen, Ger- [5 ABSTRACT This implement comprises anupright standard and a cross bar which extends at right angles to thestandard and is adjustable to'different heights along the stan- [22]Filed: Feb. 19, 1971 dard and also in its axial direction so that itstool-carryin end may be extended to different distances from [21 Appl'116796 the s tandard. The invention provides that the cross bar is madeof a tubular shape with closed ends which are [30] Foreign ApplicationPriority Data connected to each other by bracing means, for example, tierods, which extend longitudinally through the [7 3] Assignee: C.Stiefelmayer KG, Esslingen, Germany Feb. 26, 1970 Germany ..P 2008 948.9hollow inside of the cross bar and at least one of which is connected toat. least one end of thecrossbar 148/124 33/169 2 at a point above thelongitudinal axis of the cross bar thth d th 58 Field at Search..24s/12s, 124,295, 287; 3 w mung means cm 6 outside of one end of thecross bar, the tool-carrying part will be given a biasing tension whichtends to curve this part upwardly and thereby counteracts the 85/1 T;52/223 R; 33/169 R [56] Ree'ences Cited tendency of this part to benddownwardly under its UNITED-STATES PATENTS own weight and the weight ofthe respective tool thereon. This biasing tension of the cross bar maybe 1,302,293 4/ 1919 Blazer ..52/223 R adjusted in accordance with theweight of the particu- 3,097,568 7/ I963 Kampmeier ..248/ 125 too],By'providing several tie rods or similar brac- Kjell-Betger R v mean thecross bar and connecting them at 3,349,526 10/1967 Schuster ..-...s2 10sdifferentv points to-the ends of the cross bar, and

3,501,840 3/1970 QSchiler ..33/l69 R j g them axially to differenttensions, the cross a may also be bent in lateral directions.

12Clairns, 10 Drawing Figures Patented Mgrch 27, 1973 3,722,842

2 Sheets-Sheet 1 F ig] III i 31 INVENTOR. MAuu Scuueazsk MQJKM Jam;

Patented March 27, 1973 I 3,722,842

2 Sheets-Sheet 2 Fig.6 h

Fig.70 I

INVENTOR. Hsam uu Sam/E1 Maxim IMPLEMENT FOR MEASURING OR MARKINGWORKPIECES The present invention relates to an implement for measuringor marking workpieces which comprises an upright standard and a crossbar which is adjustable along this upright and also substantiallyhorizontally in the direction of its longitudinal axis relative to thestandard and is substantially hollow between its opposite ends andprovided at the inside thereof with bracing means which extend from oneof its closed ends to the other and are adapted to be variably tightenedso as to insure that the axis of the cross bar will extend in a straightdirection.

Such implements which are also known, for example,

as three-dimensional layout devices are provided with a base which isslidable along the upper surface of a work table and carries an uprightmeasuring standard which extends vertically to the upper surface of thework table and on which a slide member is adjustable to differentheights which, in turn, permits the cross bar to be adjusted todifferent effective lengths in its axial direction parallel to the uppersurface of the work table. Since for marking or measuring largeworkpieces, for example, car bodies, such a work table may have a verylarge size, for example a length of 6 meters and a width of 2.5 meters,the cross bar which carries a tool head on one end may also be requiredto have a considerable length. When such a cross bar is shiftedhorizontally in the slide member, the disadvantage occurs that thefarther its end carrying the tool head is spaced from the slide member,the more this end will bend downwardly so that the actual height of thetool head will then no longer correspond to the height of the cross baras indicated on the standard. This disadvantage may be overcome bymaking the cross bar of such an initially curved shape that, regardlessof the distance to which the tool head is extended from the standard andthe slide member thereon, it will always remain within the samehorizontal plane. This will be.

difficult to curve the cross bar so accurately that its inherentresilience will compensate the difference in weight caused by varyingits effective length.

In order to eliminate the marking or measuring inaccuracies of such animplement the cross bar of which is not initially curved upwardly asmentioned above or to eliminate the difficulties of producing such acurved cross bar, an implement has already been designed which is of atype of construction as mentioned at the beginning and is provided atthe inside of the hollow cross bar with a bracing element consisting ofa relatively thick rod which extends longitudinally from one closed endof the cross bar to the other and has pistonshaped enlargements on itsopposite ends which are in engagement with the inner peripheral wall ofthe cross bar. Approximately at the center of its length, the wall ofthe hollow cross bar is provided with a setscrew which when tightenedpresses transversely against the longitudinal rod. Since thepiston-shaped ends of this rod engage upon the inner wall of the crossbar, the screw when tightened is supposed to bend the cross arm betweenits ends in the direction opposite to the tendency of the extended crossarm to bend under its own weight and the weight of the tool thereon.Additional screws which connect the cross bar to the pistonshaped endsof the longitudinal rod lirnitany movements of these ends relative tothe cross bar.

It is one of the disadvantages of this manner of bracing the cross barthat, in order to produce the resilient bending forces upon the crossbar, the longitudinal rod at the inside of the cross bar has to berelatively thick and solid. Considering its length, this rod istherefore also very heavy, whereas properly it should be as light aspossible in order to reduce as much as possible the tendency of thecross bar to bend downwardly due to its own weight and the weight of thetool thereon. Furthermore, since in order to be able to bend the crossbar by the pressure of the central set-screw laterally against thelongitudinal rod at the inside of the cross bar, the wall of the crossbar has to be made relatively thin, there is considerable danger thatthe setscrew when tightened will cause the cross bar to be permanentlyand not merely resiliently deformed.

It is an object of the present invention to provide an implement of thetype as mentioned at the beginning which is provided with bracing meansat the inside of the hollow cross bar which are adapted to counteractthe tendency of the cross bar and the tool on its free end to benddownwardly from the upper surface of the work table when the cross baris shifted 'in its axial direction so as to increase its effectivelength from the slide member in which it is supported on the standard. Afurther object of the invention is to provide such bracing means whichare of a simple construction and a light weight and may be easilyadjusted, for example, in accordance with different weights of the toolswhich may be removably secured in place of each other to the tool holderon the free end of the cross bar.

For attaining these objects, the invention provides these bracing meansto consist of at least one bracing element, preferably in the form of atension element such a tie rod or similar means, which acts upon theaxially outer ends of the crossbar and the bracing action of which uponthe cross bar may be easily increased or reduced at will. By thesebracing means it is possible in accordance with the principle ofprestressed concrete to apply a lower or higher longitudinal forceeccentrically upon the cross bar and thereby to tend to curve thelongitudinal axis of the latter to different extents so as to counteractthe tendency of the tool-carrying end of the cross bar to benddownwardly and to insure that the measuring or marking point of the toolwhich is secured to the tool head on the end of the cross bar willremain with a sufficient accuracy within the same horizontal planeregardless of the length to which the cross bar is extended from theslide member which supports it rigidly on the standard.

The bracing meansaccording to the invention may consist of relativelythin and light elements since they only have to transmit forces in theirlongitudinal directions, while no elastic or other forces have to beexerted in the transverse direction of the cross bar. The tension orpressure is applied upon the outer ends of the cross bar and there areno adjusting elements which extend transversely through the cross barand might permanently deform its cross-sectional shape. It is thereforenot only possible to make the bracing elements in toto thinner and of alighter weight than the bracing element which was previously requiredbut the walls of the cross bar may also be made relatively thin. Theadvantages of the invention are especially great if the bracing meansmerely consist of tension elements and if it is only necessary to applya tension upon the ends of these elements. It is, however, also possibleaccording to the invention to attain the desired longitudinal bracingeffect by pressure elements which do not necessarily have to beconsiderably thicker than the tension elements if, for example, byproviding several transverse supports within the cross bar. at shortdistances from .each other, the unsupported length of these pressureelements within which buckling could occur is made very small.

According to an improved embodiment of the invention, the hollow crossbar is provided with at least two bracing elements which are locatedtherein above each other and one of which has at least one end actingupon one axial end of the cross bar at a level above the iongitudinalaxis of the cross bar, while the other bracing element has at least oneend acting upon an axial end of the cross bar at a level below thisaxis. If both bracing elements are tightened, the upper element willcounteract the lower element within a vertical plane so that bothbracing elements will be under an initial tension or pressure, wherebyineffective initial motions due to an inherent expansion or compressionof the material of the bracing elements will be prevented. When thesebracing elements are adjusted, they will therefore imvmediately act uponthe cross bar and affect the direction of its longitudinalaxis and donot at first need to overcome a certain play in their longitudinaldirections.

According to another important feature of the invention, the hollowcross bar contains at least two bracing elements laterally adjacent toeach other within the same horizontal plane. At'least one end of one ofthese bracing elements acts upon the corresponding axial end of thecross bar at a point at the left side of the longitudinal axis of thecross bar, while at least one end of the other bracing element acts uponthe respective axial end ofthe cross bar at a point at the right side ofthe central vertical plane of this bar. By tightening these bracingelements to different extents, it is possible to affect the straightnessof the cross bar also within a horizontal plane which is importantespecially for compensating tolerances of manufacture of the cross bar.

Another important feature of the invention consists in providing atleast three bracing elements preferably in an isosceles triangulararrangement within the hollow cross bar so that two of these elementsare disposed laterally adjacent to each other within thesametransversely horizontal planes. Such a triangular arrangement of thebracing elements permits not only an adjustment of the desired initialtension or pressure so as to counteract the tendency of the cross bar tobend downwardly but also an adjustment of the direction of the cross barwithin a horizontal plane.

If the bracing means in the form of one or more elements are disposedparallel to the longitudinal axis of the cross bar and are tightened,the cross bar will be bent to an arcuate shape. It has now been foundthat the best possible compensation of the curvature of the cross barwhich is caused by its weight and the weight of the tool thereon may beattained if by being tightened at its ends the cross bar will beinitially bent to a parabolic curvature which, as seen from its endcarrying the tool head, is at first very flat and only thereafterincreases in slope toward the other rear end. Another very importantfeature of the invention for attaining such a parabolic shape consistsin mounting the bracing element or at least one of the bracing elementsto extendat an oblique angle to the longitudinal axis of the cross bar.In a preferred embodiment of the invention the point of connection ofthe obliquely extending bracing element or of each of these elements tothe free end of the cross bar carrying the tool head is located within alower plane than its point of connection to the other end of the crossbar. Thus, for example, the first point of connection may be located atthe level of the longitudinal axis of the cross bar, while the secondpoint of connection at the rear end of the cross bar may be locatedabove this axis. The parabolic curvature of the cross bar then mergesinto a straight line near the free end of the cross bar carrying thetool head.

It has further been found that, when the effective length of the crossbar is increased, it will due to its inherent rigidity remain at firststraight and will start to curve downwardly only at a certain distancefrom its rigidly clamped part. For ideally compensating this bending ofthe cross bar, the biasing curvature of the latter would have to extendinversely corresponding to the normal curvature, that is, from the freeend of. the cross bar at first horizontally and, for example, onlysubsequent to its center in the form of an upwardly directed paraboliccurve. This ideal shape of the cross bar would be attainable if theoblique longitudinal bracing means would extend, for example, only up toa central part of the length of the cross bar where the bracing meanswould end on the central'longitudinal plane of the cross bar. This,however, can only be attained with difficultiessince it would then benecessary to provide and secure a special central support within thecross bar. According to a further embodiment of the invention, acompromise solution of this difficulty may be attained by placing theaxial point or points of connection of the oblique bracing means to thefree end of the cross bar carrying the tool head in a positionunderneath the level of the longitudinal axis of the cross bar, whilethe point or points of connection of these bracing means to the otherend of the cross bar are located above this plane. In this manner it ispossible to attain a biasing curvature of the cross bar of a slightlywavy shape insofar as it extends at first in accordance with the idealparabolic shape, while the subsequent length of the cross bar toward itsfree end will be slightly wavy and deviate only very slightly from thedesired straight shape. The present invention therefore attains thealmost ideal conditions without requiring any additional structuralmeans. These parabolic or first parabolic and subsequently slightly wavybiasing curvatures are only attainable because the longitudinal bracingmeans according to the invention are located at the inside of the crossbar and can thus extend obliquely from one end of the cross bar to whichthey are connected above the longitudinal axis of this bar to the otherend to which they are connected below this axis.

If the bracing means consist of several bracing elements, the positionsof their axial connecting points are determined by the resultant vectorof these points. If three bracing elements are provided in a triangularformation in which two of these elements are located within the upperpart and the third within the lower part of the cross-sectional area ofthe inside of the cross bar, it is advisable that only the two upperelements extend obliquely to the longitudinal axis of the cross bar,while the'lower element extends substantially parallel to this axis.

The features and advantages of the present invention will become furtherapparent from the following detailed description thereof which is to beread with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 shows a side view of the implement according to the invention andof a part of the work table;

FIG. 2 shows a longitudinal section of one end of the cross bar of theimplement according to FIG. 1 but on a larger scale;

FIG. 3 shows across section which is taken along the line Ill III ofFIG. 2;

FIG. 4 shows a longitudinal section of the cross bar according to FIGS.2 and 3, and a compression and tension diagram therein;

FIG. 5 shows an illustration similar to FIG. 4 of the cross baraccording to a modification of the invention;

FIG. 6 shows a diagram of the line of downward deflection of a cross bardue to its weight; while FIGS. 7 to show diagrams of different biasinglines along which the cross bar may be bent so as to compensate itsnormal deflection; namely, FIG. 7 a biasing line of the ideal parabolicshape, FIG. 8 a biasing line of a convex shape which deviatesconsiderably from the ideal line, FIG. 9 a biasing line of a parabolicshape 7 which is more similar to the ideal line, and FIG. 10 a biasingline of a wavy shape which is closely similar to the shape of the idealline. i

In the drawings, FIG. 1 illustrates a work table 1 which has an uppersurface 2 upon which the workpiece is placed or clamped which is to bemeasured or marked. At one end of the opposite lateral surfaces 3 and 4of work table 1 a pair of flat bars 5 are secured which are providedwith corresponding recesses 6 into which a locking member 8 on each endofa guide bar 7 is adapted to engage which extends across the work table1.

Along the guide bar 7 the implement according to the invention is guidedwhich is generally designated by the numeral 10. It comprises a base 11which is slidable on the work table 1 and on which an upright supportingmeans including a standard 12 is mounted which extends vertically to theupper surface 2 of work table 1. The supporting means further comprisesa slide member 13 which is adjustable to different heights along thestandard 12 and forms a horizontal guide means for a cross bar 14 whichextends through this slide member and is adjustable thereon in its axialdirection parallel to the upper surface 2 of work table 1. The front endof this cross bar 14 is provided with a tool head 15 for holding ameasuring or marking tool 16 which may also be exchanged for a differenttool. The rear end is located on the other side of guiding slide member13. Standard 12 is provided with a groove into which a scale bar 17 isfitted, and cross bar 14 is likewise provided with a groove into which ascale bar 23 is fitted. Slide member 13 is further provided with avernier 24 for reading its vertical position on scale bar 17 and with avernier 25 for reading the horizontal position of cross bar 14 on scalebar 23.

As illustrated in FIGS. 2 and 3, cross bar 14 has a rectangular tubularshape and itsv opposite ends are closed by end plates 29. Above itslongitudinal axis 77, cross bar 14 contains within its inner upper parttwo bracing elements in the form of tie rods 30 and within its innerlower part underneath the axis 77 one bracing element likewise in theform of a tie rod 31. These three tie rods extend along straight linesfrom the tool supporting front end to the rear from one to the other endof cross bar 14 and are provided on both ends with threaded parts 32which project through bores in the end plates 29. As may be seen in FIG.3, the three tie rods 30 and 31 are disposed relative to each other soas to be located at the corners of an isosceles triangle. The outer sideat least of. the left end plate 29 carries presetting means in the formof nuts 33 which are screwed upon the threaded end parts 32 of the tierods and permit these rods to be differently prestressed from theoutside so as to bend the tubular cross bar 14 upwardly, and then to belocked permanently for compensating its tendency to bend downwardlyunder its own weight and the weight of the tool 16. Due to thetriangular arrangement of the three tie rods, it is also possible tobend the cross bar 14 slightly in lateral directions if this should bedesirable, especially for compensating tolerances of manufacture ofcross bar FIG. 4 illustrates this cross bar 14 once morediagrammatically. The points on which the tie rods 30 and 31 are to betightened at the left end 73 of cross bar 14 which extends through theslide member 13 as shown in FIG. 1 are indicated at 75, while at theother end 74 which carries the tool head 15 these points are indicatedat 76. The nuts 33 as shown in FIG. 2 only need to be screwed upon oneend of the tie rods, for example, the end 73, while the other ends ofthe tie rods may be screwed into the other end plate 29 or be rigidlysecured thereto. This other end plate may also be integral with the toolholder 15.

FIG. 5 illustrates a modification of the tubular cross bar 14 whichlikewise contains three tie rods 30 and 31 in a triangular arrangementsimilar to that as shown in FIGS. 2 to 4 so that the two tie rods 30 arelocated within the upper part above the longitudinal axis 77 of crossbar 14 and one tie rod 31 within the lower part below the axis 77. Fromthe left end 73 of cross bar 14 toward the tool head 15 the two uppertie rods 30 extend obliquely downwards approximately to the level of thelongitudinal axis 77 of cross bar 14, while the lower tie rod 31 extendsparallel to the axis 77 like the lower tie rod in FIGS. 2 to 4. Thepoints of connection 76 of the upper tie rods 30 to the end 74 of crossbar 14 which carries the tool head 15 are therefore disposed on a lowerlevel than their points of connection 75 to the opposite end 73 of thecross bar. The same applies if only the resultant vector of the threetie rods and the three points of connection at each end is considered.The four pressure and tension diagrams A, B, C and D in FIG. 5illustrate that, due to this course or arrangement of the tie rods, itis possible to tighten them so as to provide the cross bar 14 with aparabolic curvature the first part of which following the end 74 is veryflat, while the subsequent part increases in slope toward the end 73. Bydifferently adjusting the two upper tie rods 30 it is also possible tocorrect small inaccuracies of the cross bar 14 within a horizontalplane.

If the adjustment of the shape of cross bar 14 is carried out in such amanner that the lower tie rod 31 is provided with a small initialtension, it will only be necessary for a further later adjustment toturn the nut 33 of this tie rod in order to attain the desired shape ofthe cross bar.

Of course, in place of tie rods, it is also possible to provide othersuitable kinds of tension elements, for example, cables. Furthermore,for attaining a desired parabolic shape of cross bar 14, it is alsopossible to provide the tension elements in other inclined positions,for example, so that the axial points of connection 76 of the obliquelyextending elements 30 on the end 74 of cross bar 14 adjacent to the toolhead will be located within a plane underneath the longitudinal axis 77of cross bar 14.

In each of FIGS. 6 to 10, the solid line indicates on a scale of 1 to 10the theoretic horizontal direction of cross bar 14, while thedot-and-dash line indicates on a scale of 100 to 1 the course of a linealong which it is bent within a vertical plane so as to have therequired initial tension.

In FIG. 6, the dot-and-dash line 79 indicates at the points 3 to 13,respectively, the extent to which the tool-head end of the unbracedcross bar 14 is bent when it projects to each of eleven differentpositions from the slide member 13, as shown in FIG. 1. Cross bar 14extends, for example, within the slide member 13 up to the position 78between the points 2 and '3. Due to its inherent rigidity, cross bar 14will remain straight when being pulled out of slide member 13 up to thepoint 7. However, when pulled out beyond this point, it will benddownwardly so that its right end will be located at the points 8' to 13,respectively. This results in a parabolic curvature of cross bar 14 fromthe point 13 to the point 7 from which it extends horizontally up to thepoint 1.

For compensating this curvature ideally, it would be necessary toprebend the cross bar 14 to a shape as indicated in FIG. 7 by thedot-and-dash line 80, that is, the right part from the point 13 to thepoint 7 in a straight direction and then to the left end from the point7 to the point 1 along an upwardly directed parabolic curve whichinversely corresponds to the curved line 79 between the points 13 and 7in FIG. 6.

This ideal line 80 of the curvature of cross bar 14 would I beattainable if its longitudinal bracing means would extend obliquely fromthe left end only up to a central part of the length of the cross barand would end at that point on the longitudinal axis of the cross bar.This can, however, be attained only with difficulties since the crossbar would then require a special support at its center.

If the bracing elements extend parallel to the longitudinal axis 77 ifthe cross bar within the upper part of the hollow inside thereof, thecross bar will be bent downwardly along an arc to a convex shapefasindicated in FIG. 8 by the dot-and-dash line 81. It will be seen thatthe right upwardly curving part of line 81 deviates from thecorresponding straight part of the ideal line as shown in FIG. 7.

If the longitudinal bracing means extend from the upper left endobliquely toward the right up to the longitudinal axis 77 of the crossbar, the latter will be parabolically prebent up to its right end, asindicated by the dot-and-dash line 82 in FIG. 9. This prebent curvatureis also not as good as desirable because it is curved too stronglyespecially between the points 3 and 7.

If, however, the longitudinal bracing means extend from the upper leftobliquely downwards toward the right to a point slightly below thelongitudinal axis 77 of the cross bar, the latter will be prebent to aslightly wavy shape, as indicated by the dot-and-dash line 83 in FIG.10. The left part of this curved line extends from the points 1 to 7 inaccordance with the corresponding part of the ideal parabolic line 80 asshown in FIG. 7, while the wavy right part of line 83 deviates only veryslightly from the ideal straight line. The partly parabolic and thenslightly wavy line 83 as shown in FIG. 10 is therefore the most similarto the ideal line according to FIG. 7.

The bracing possibilities according to FIGS. 9 and 10 are possible onlybecause the longitudinal bracing means according to the invention arelocated at the inside of the tubular cross bar so that the obliquelyextending bracing means may be connected at one end above the axis 77and at the other end below the axis 77 of the cross bar to therespective axial ends of the latter.

Although my invention has been illustrated and described with referenceto the preferred embodiments thereof, I wish to have it understood thatit is in no way limited to the details of such embodiments but iscapable of numerous modifications within the scope of the appendedclaims.

Having thus fully disclosed my invention, what I claim is:

1. An implement for measuring workpieces, comprising upright supportingmeans including horizontal guide means; a tubular cross bar having anaxis, a tool supporting front end, and a rear end, said cross bar beingsupported in said guide means intermediate said ends for horizontalmovement in the direction of said axis between displaced positions inwhich said tool supporting end is spaced different axial distances fromsaid guide means so that said tool supporting end is urged by the forceof gravity downward out of a desired horizontal level to differentdegrees depending on the length of the respective distance; and bracingmeans including at least one bracing element located within said tubularcross bar spaced from said axis and having a cross section substantiallysmaller than the cross section of said tubular cross bar, and oppositeends connected with said front and rear ends of said cross bar,respectively, said bracing element extending along a straight linedirectly between said front and rear ends, and adjustable presettingmeans at least at one end of said bracing element abutting said crossbar so that said bracing ele-' ment is tensioned along said straightline, said presetting means including means holding said bracing elementpermanently prestressed for holding said cross bar permanently curvedirrespective of the length of said axial distances so that the effect ofthe force of gravity is substantially compensated and said toolsupporting end is substantially located at said desired horizontal levelirrespective of the position of said cross bar relative to said guidemeans.

2. An implement as claimed in claim 1 wherein said bracing means includeat least two bracing elements located within said tubular cross bar, andbeing permanently prestressed by said presetting means, at least one endof one of said bracing elements being connected with the correspondingend of said cross bar at a point located above the horizontal level ofsaid longitudinal axis of said cross bar, and at least one end of theother bracing element being connected to said one end of said cross barat a point below the horizontal level of said axis, the other ends ofsaid bracing elements being connected with the other end of said crossbar, said prestressed bracing elements being adapted to counteract eachother. I

3. An implement as claimed in claim 1 in which said bracing meansinclude at least two bracing elements disposed laterally adjacent eachother in a direction transverse to said axis, at least one end of one ofsaid bracing element acting on the correspondingend of said cross bar ata point at the left side of a vertical plane passing through said axisof said cross bar, and at leastone end of the other bracing elementacting upon the corresponding of said cross bar at a point at theright'side of said central vertical plane.

4. An implement as claimed in claim 1 in which said bracing meansinclude at least three bracing elements prestressed by said presettingmeans and extending within said cross bar between the ends of the same,the ends of said bracing element at least at one end of said cross barbeing located at the corners of an imaginary triangle, at least two ofsaid bracing elements being disposed laterally adjacent each other in adirection transverse to the direction of said axis, and at oppositesides of a central vertical plane passing through said axis of saidcross bar.

5. An implement as claimed in claim 4 in which at least said ends ofsaid bracing element are located at the corners of an imaginaryisosceles triangle.

6. An implement as claimed in claim 4 in which one end of each of saidtwo laterally adjacent bracing elements are connected with thecorresponding end of said cross bar at the level above said axis of saidcross bar, and one end of the third bracing element is connected withthe corresponding end of said cross bar at a level below said axis ofsaid cross bar.

7. An implement as claimed in claim 6 in which said two laterallyadjacent bracing elements extend within said cross bar slanted atsubstantially equal oblique angles to said axis of said cross bar atleast a greater part of the length of said bracing elements beinglocated above said axis, and wherein said third bracing element extendssubstantially parallel to said axis of said cross bar.

8. An implement as claimed in claim 1 wherein said one bracing elementextends within said cross bar slanted at an angle to said axis of saidcross bar.

9. An implement as claimed in claim 8 wherein the greater part of thelength of said slanted bracing element is located above said axis ofsaid cross bar;

10. An implement as claimed in claim 8 wherein one end of said slantedbracing element is connected with said tool-supporting end of said crossbar, and the other end of said bracing is connected with said rear endof said crossbar, said one endvof said bracing element being disposed ina lower position than said other end of said bracing element.

11. An implement as claimed in claim 10 wherein said one end of saidbracing element is disposed below the horizontal level of said axis ofsaid cross bar, and wherein said other end of said bracing element isdisposed above the horizontal level of said axis of said cross bar.

12. An implement as claimed in claim 11 wherein said bracing elementincludes a tie rod having ends connected with said front and rear endsof said cross bar, at least one of said ends being threaded andextending through the corresponding end of said cross bar, and whereinsaidpresetting means comprise a nut screwed 'from the outside of saidcross baron said threaded end and abutting the corresponding end of saidcross bar.

1. An imPlement for measuring workpieces, comprising upright supportingmeans including horizontal guide means; a tubular cross bar having anaxis, a tool supporting front end, and a rear end, said cross bar beingsupported in said guide means intermediate said ends for horizontalmovement in the direction of said axis between displaced positions inwhich said tool supporting end is spaced different axial distances fromsaid guide means so that said tool supporting end is urged by the forceof gravity downward out of a desired horizontal level to differentdegrees depending on the length of the respective distance; and bracingmeans including at least one bracing element located within said tubularcross bar spaced from said axis and having a cross section substantiallysmaller than the cross section of said tubular cross bar, and oppositeends connected with said front and rear ends of said cross bar,respectively, said bracing element extending along a straight linedirectly between said front and rear ends, and adjustable presettingmeans at least at one end of said bracing element abutting said crossbar so that said bracing element is tensioned along said straight line,said presetting means including means holding said bracing elementpermanently prestressed for holding said cross bar permanently curvedirrespective of the length of said axial distances so that the effect ofthe force of gravity is substantially compensated and said toolsupporting end is substantially located at said desired horizontal levelirrespective of the position of said cross bar relative to said guidemeans.
 2. An implement as claimed in claim 1 wherein said bracing meansinclude at least two bracing elements located within said tubular crossbar, and being permanently prestressed by said presetting means, atleast one end of one of said bracing elements being connected with thecorresponding end of said cross bar at a point located above thehorizontal level of said longitudinal axis of said cross bar, and atleast one end of the other bracing element being connected to said oneend of said cross bar at a point below the horizontal level of saidaxis, the other ends of said bracing elements being connected with theother end of said cross bar, said prestressed bracing elements beingadapted to counteract each other.
 3. An implement as claimed in claim 1in which said bracing means include at least two bracing elementsdisposed laterally adjacent each other in a direction transverse to saidaxis, at least one end of one of said bracing element acting on thecorresponding end of said cross bar at a point at the left side of avertical plane passing through said axis of said cross bar, and at leastone end of the other bracing element acting upon the corresponding ofsaid cross bar at a point at the right side of said central verticalplane.
 4. An implement as claimed in claim 1 in which said bracing meansinclude at least three bracing elements prestressed by said presettingmeans and extending within said cross bar between the ends of the same,the ends of said bracing element at least at one end of said cross barbeing located at the corners of an imaginary triangle, at least two ofsaid bracing elements being disposed laterally adjacent each other in adirection transverse to the direction of said axis, and at oppositesides of a central vertical plane passing through said axis of saidcross bar.
 5. An implement as claimed in claim 4 in which at least saidends of said bracing element are located at the corners of an imaginaryisosceles triangle.
 6. An implement as claimed in claim 4 in which oneend of each of said two laterally adjacent bracing elements areconnected with the corresponding end of said cross bar at the levelabove said axis of said cross bar, and one end of the third bracingelement is connected with the corresponding end of said cross bar at alevel below said axis of said cross bar.
 7. An implement as claimed inclaim 6 in which said two laterally adjacent bracIng elements extendwithin said cross bar slanted at substantially equal oblique angles tosaid axis of said cross bar at least a greater part of the length ofsaid bracing elements being located above said axis, and wherein saidthird bracing element extends substantially parallel to said axis ofsaid cross bar.
 8. An implement as claimed in claim 1 wherein said onebracing element extends within said cross bar slanted at an angle tosaid axis of said cross bar.
 9. An implement as claimed in claim 8wherein the greater part of the length of said slanted bracing elementis located above said axis of said cross bar.
 10. An implement asclaimed in claim 8 wherein one end of said slanted bracing element isconnected with said tool-supporting end of said cross bar, and the otherend of said bracing is connected with said rear end of said cross bar,said one end of said bracing element being disposed in a lower positionthan said other end of said bracing element.
 11. An implement as claimedin claim 10 wherein said one end of said bracing element is disposedbelow the horizontal level of said axis of said cross bar, and whereinsaid other end of said bracing element is disposed above the horizontallevel of said axis of said cross bar.
 12. An implement as claimed inclaim 11 wherein said bracing element includes a tie rod having endsconnected with said front and rear ends of said cross bar, at least oneof said ends being threaded and extending through the corresponding endof said cross bar, and wherein said presetting means comprise a nutscrewed from the outside of said cross bar on said threaded end andabutting the corresponding end of said cross bar.